REFLECTOR:AC 91-75
Jack Hayes
reflector@tvbf.org
Sat, 13 Dec 2003 18:09:37 -0500
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Question: I've heard of a recent FAA advisory circular (AC) that =
discusses the merits of replacing a rate-of-turn indicator with a second =
attitude indicator. Do you know which AC this is and how I can access =
it?
Answer: You are referring to AC 91-75, dated June 25, 2003, that can be =
downloaded from AOPA Online. The purpose of the AC is to provide a =
method to substitute an approved attitude indicator for the rate-or-turn =
indicator mandated by FAR 91.205(d)(3). There are exclusions listed in =
the AC, and it applies to Part 23-certificated aircraft weighing less =
than 12,500 pounds and operating under Part 91. A recommendation from an =
FAA and industry study indicated that vacuum system failures play a =
significant role in fatal accidents during instrument meteorological =
conditions. Because vacuum system or gyro failure is insidious, it is =
difficult to recognize. A second attitude indicator (with an independent =
power source) would provide redundant information and be less confusing =
during partial panel operations. As with all advisory circulars, this is =
a recommendation; it's not mandatory.=20
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<DIV><FONT size=3D2><STRONG>Question:</STRONG> I've heard of a recent =
FAA advisory=20
circular (AC) that discusses the merits of replacing a rate-of-turn =
indicator=20
with a second attitude indicator. Do you know which AC this is and how I =
can=20
access it?<BR><BR><B>Answer:</B> You are referring to AC 91-75, dated =
June 25,=20
2003, that can be downloaded from </FONT><A=20
href=3D"http://download.aopa.org/epilot/2003/ac91-75.pdf"><FONT =
size=3D2>AOPA=20
Online</FONT></A><FONT size=3D2>. The purpose of the AC is to provide a =
method to=20
substitute an approved attitude indicator for the rate-or-turn indicator =
mandated by FAR 91.205(d)(3). There are exclusions listed in the AC, and =
it=20
applies to Part 23-certificated aircraft weighing less than 12,500 =
pounds and=20
operating under Part 91. A recommendation from an FAA and industry study =
indicated that vacuum system failures play a significant role in fatal =
accidents=20
during instrument meteorological conditions. Because vacuum system or =
gyro=20
failure is insidious, it is difficult to recognize. A second attitude =
indicator=20
(with an independent power source) would provide redundant information =
and be=20
less confusing during partial panel operations. As with all advisory =
circulars,=20
this is a recommendation; it's not mandatory. =
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